Would be nice to have
Glad this is something you’d like to see. We already have that — I guess we need to do a better job surfacing it :)
When you open the manual focus slider (by tapping on the AF
icon to the left of the bottom bar), tap the little icon with an eye right next to the slider. The areas in focus will light up in green. We will add a little notification when turning it on/off, similar to when changing exposure bias for example.